The notation "φ(6)" refers to the Euler's totient function, which counts the number of positive integers up to a given integer that are relatively prime to it. For the number 6, the integers less than 6 are 1, 2, 3, 4, and 5. Among these, the numbers that are relatively prime to 6 are 1 and 5. To calculate φ(6), we find that there are 2 integers (1 and 5) that do not share any common factors with 6, other than 1. Therefore, φ(6) equals 2. This function is significant in number theory and has applications in areas such as cryptography and modular arithmetic.